In your case lets say you log into profile 1, you are signed into the browser and have all your add-ons and bookmarks. You create a second profile on the same desktop and want the same add-ons and bookmarks to show for your second account. You would then log into the browser and then everything would load into the browser.

What is your reason to use Sync ?

Adding more devices to Sync is optional. Your Firefox Sync account has been created when you see the page to add another device. You can close this tab if you do not want or can't add another (mobile) device. Note that Sync is not meant as a backup, but is meant to merge/share data among other devices.

Thank you everyone for the support! really do appreciate you!!!

I just created an account and Firefox will not let me pass the requirement to sync another device, which I don't have.

Hi f67Jugliz

Setting up Sync on your device has finished if you get this page. All you need to do is closing the tab where you are asked to add another device.